docs: def serialize_iter(self, data, iter_type, div=None, **kwargs):
          """Serialize iterable.
  
          Supported kwargs:
          serialization_ctxt dict : The current entry of _attribute_map, or same format. serialization_ctxt['type'] should be same as data_type.
  
          :param list attr: Object to be serialized.
          :param str iter_type: Type of object in the iterable.
          :param bool required: Whether the objects in the iterable must
           not be None or empty.
          :param str div: If set, this str will be used to combine the elements
           in the iterable into a combined string. Default is 'None'.
          :rtype: list, str
          """
          if isinstance(data, str):
              raise SerializationError("Refuse str type as a valid iter type.")
  
          serialization_ctxt = kwargs.get("serialization_ctxt", {})
  
          serialized = []
          for d in data:
              try:
                  serialized.append(self.serialize_data(d, iter_type, **kwargs))
              except ValueError:
                  serialized.append(None)
  
          if div:
              serialized = ['' if s is None else str(s) for s in serialized]
              serialized = div.join(serialized)
  
          if 'xml' in serialization_ctxt:
              # XML serialization is more complicated
              xml_desc = serialization_ctxt['xml']
              xml_name = xml_desc['name']
  
              # Create a wrap node if necessary (use the fact that Element and list have "append")
              is_wrapped = "wrapped" in xml_desc and xml_desc["wrapped"]
              node_name = xml_desc.get("itemsName", xml_name)
              if is_wrapped:
                  final_result = _create_xml_node(
                      xml_name,
                      xml_desc.get('prefix', None),
                      xml_desc.get('ns', None)
                  )
              else:
                  final_result = []
              # All list elements to "local_node"
              for el in serialized:
                  if isinstance(el, ET.Element):
                      el_node = el
                  else:
                      el_node = _create_xml_node(
                          node_name,
                          xml_desc.get('prefix', None),
                          xml_desc.get('ns', None)
                      )
                      if el is not None:  # Otherwise it writes "None" :-p
                          el_node.text = str(el)
                  final_result.append(el_node)
              return final_result
          return serialized